Question: When was the party membership formed by Atal Bihari Vajpayee?
Paraphrase: At what point was the party membership formed by Atal Bihari Vajpayee?
SPARQL (Wikidata): SELECT ?answer WHERE { wd:Q233289 wdt:P102 ?X . ?X wdt:P571 ?answer}
Answer: 1980-01-01T00:00:00Z, 1951-01-01T00:00:00Z